Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$54.72	8.253%	$59.236	$59.24	$59.25	$59.20
Purchase #2	$47.54	11.372%	$52.9462	$52.95	$52.95	$52.90
Purchase #3	$188.32	11.723%	$210.3968	$210.40	$210.40	$210.40
Purchase #4	$130.75	11.333%	$145.5679	$145.57	$145.55	$145.60
Purchase #5	$208.78	10.266%	$230.2134	$230.21	$230.20	$230.20
Purchase #6	$122.46	11.271%	$136.2625	$136.26	$136.25	$136.30
Purchase #7	$55.90	3.729%	$57.9845	$57.98	$58.00	$58.00
7 purchase totals =	$808.47		$892.6073	$892.61	$892.60	$892.60